Examples of such currently-used apparatus include an inkjet printing apparatus (also referred to as an image recorder). The printing apparatus includes a transport mechanism transporting web paper (web), and inkjet heads each discharge ink (ink droplets) onto the web paper to be transported for printing images. For instance, four inkjet heads are provided in a transportation direction of the web paper, and discharge ink in four colors individually for color printing.
The web paper sometimes serpentines when the transport mechanism transports the web paper. Such serpentine web paper causes misregister that an actual printing position is shifted from a target printing position. This causes a color shift that printing positions for different colors shift relative to one another. There has been disclosed a method of performing registration by moving the inkjet heads (printing heads) in accordance with detection values by edge sensors or a method of conform the color shift by shifting printing data for adjusting the misregister or the color shift generated in the above manner. See, for example, Japanese Unexamined Patent Publication No. 2002-099178A. In Japanese Unexamined Patent Publication No. 2002-099178A, a position of forming a latent image by an electro photographic printing apparatus is corrected.